In a photographic plate-making process, a step to convert a document with continuous gradation to dot images is included. For this step, a technology employing infectious development has been used as a photographic technology capable of offering super high contrast image reproduction.
Litho-type silver halide photographic light-sensitive materials used for infectious development are, for example, composed of silver bromochloride emulsion having an average grain size of 0.2 .mu.m and high silver chloride content ratio (at least 50 mol % or more) wherein grain size distribution is narrow and the shape of grain is uniform. By processing the above-mentioned litho-type silver halide photographic light-sensitive material with an alkaline hydroquinone developing solution with low sulfite ion density, images having high contrast, high sharpness and high resolution can be obtained.
However, since the above-mentioned litho-type developing solutions are subjected to air oxidation, it is extremely inferior in preservability. Therefore, it is also difficult to keep the quality of development constant in continuous use.
Methods for obtaining images having high contrast rapidly without employing the above-mentioned litho-type developing solutions are known. As shown in U.S. Pat. No. 2,419,975 and Japanese Patent Publication Open to Public Inspection (hereinafter, referred to as Japanese Patent O.P.I. Publication) Nos. 16623/1976, 20921/1976 and 106244/1981, it represents a method to contain hydrazine derivatives in silver halide light-sensitive materials.
Due to the above-mentioned method, sulfite ion density in a developing solution can be kept high and processing can be conducted while keeping high preservability.
However, in the above-mentioned method, processing had to be conducted with developing solution having pH of 11 or more in order to utilize the high contrast property of hydrazine derivatives to a full extent. Though developing solutions having pH of 11 or more is more stable than a litho-type developing wherein the developing agent is easily oxidized when it is exposed to air, it often fails to offer super high contrast images due to the oxidation of developing agent.
In order to complement the above-mentioned defect, silver halide photographic light-sensitive materials containing nucleating agents which make images contrast-increasing even in a developing solution with relatively low pH are disclosed in Japanese Patent O.P.I. Publication No. 29751/1988 and European Patent Nos. 333,435 and 345,025.
However, when silver halide photographic light-sensitive materials containing the above-mentioned nucleating agents are processed with developing agent having pH of less than 11, it is the present situation that contrast-increase is incomplete and satisfactory dot properties cannot be obtained.
On the other hand, in European Patent No. 364,166 and Japanese Patent O.P.I. Publication Nos. 222241/1987, 140340/1985, 250439/1987 and 280733/1987, contrast-promoting compounds for accelerating contrast-increase are described. It is sure that dot properties are improved by adding the above-mentioned compounds into emulsion layers. However, it turned out that a problem of sand-like and pinhole-like fogging in dots, so-called pepper fog, occurred damaging the quality of dot images.
Therefore, there has been demanded a light-sensitive material solving the above-mentioned problems and employing effective nucleating agents and contrast-promoting compounds.